Japanese Patent No. 3,834,326 discloses a method in which cancer cell is isolated with immunobeads and detected by, for example, immunostaining with an antibody. Japanese Patent Application Laid Open (JP-A) No. 2001-41959 discloses a method for detecting a cancer cell, including contacting a liquid containing a cancer cell with a support having an immobilized ligand that specifically binds to the cancer cell, and labeling the cancer cell bound to the support. Other known methods for detecting a cancer cell include a method in which a cancer cell is separated from a normal cell according to the size thereof and detected by immunostaining, and a method in which a cancer cell is separated from a normal cell by density gradient centrifugation and detected by immunostaining. For example, Japanese Patent No. 3,867,968 discloses a method for detecting a cancer cell contained in blood, in which the cancer cell infected with an adenovirus to express a fluorescent protein is detected.